1. Field of the Invention
The present invention relates to a polygonal image-drawing processor in three-dimensional computer graphics such as a work station, game machines, etc.
2. Description of the Related Art
Recently, various kinds of methods for providing a function of graphics have been proposed. In these methods, a three-dimensional display of a full color and a high speed numerical operation ability are required as the graphics function. For example, a graphics system IRIS 4D-MP manufactured by Silicon Graphics Computer Systems is described as a graphics work station in "Videoized machine", pp. 51 to 55 written by Mitsuo Ishii (published by Ohm Co.).
In an optical image-drawing processor used in the above-mentioned graphics system, all the data of picture elements are written to a bit map memory so that a large amount of memory capacity is required. For example, in the case of a CRT display, etc., it is necessary to read data of one picture out of the memory in 1/60 second so that a memory operated at a high speed is required and the processor is complicated and cost thereof is increased.
In a general clipping device, much time is required in clipping processing, or large hardware is required as mentioned above.
Further, in the general clipping device, the range of a receiving coordinate is set to be wider than the size of a screen region. Accordingly, it is necessary to dispose a memory having a large capacity and much memory access time is required.